The optical properties of light emitting devices based on colloidally synthesized CdSe/CdS core/shell semiconductornanocrystals embedded in vertical cavities are investigated. The cavities are several micrometers, thick and formed by a metallic mirror and a dielectric Bragg interference mirror deposited on the opposite surfaces of cleaved pristine mica sheets. Due to the large cavity length, up to 30 resonances are found within the Bragg mirror stop band. The corresponding small mode spacing allows one to extract a large portion of the broad nanocrystal luminescence band from the cavity upon optical excitation. The spontaneous emission of these cavities is highly forward directed with a beam divergence smaller than Furthermore, the emission is linearly polarized which is a result of the birefringent properties of the mica sheets.

An in-plane-type channel-drop filtering device with input/output waveguides and a point defect cavity in a two-dimensional photonic crystal slab is investigated. The in-plane operation becomes possible by employing a point defect cavity with an extremely high factor to suppress the radiation loss for the out-of-plane direction. 60° bends are also introduced in the output waveguide to avoid interference between the input/output waveguides. The transmission frequency range of the output waveguide with bends is tuned by changing the size of the air holes at the apex of the corner so that the resonant frequency of the point defect cavity is within the transmission band. A channel drop operation with a very high resolution of 0.12 nm is successfully observed at 1.55 μm wavelengths.

We demonstrate terahertz-induced lensing (TIL), the focusing and defocusing of an ultrashort “probe” laser pulse induced by a collinearly traveling terahertz pulse in an electro-optic crystal. The intensity change on the axis of the probe beam after the crystal is shown to be linear with the terahertz (THz) electric field and can thus be used to measure the THz wave form. We show that the sensitivity of TIL is comparable to conventional electro-optic sampling, with the advantage of being applicable to all classes of electro-optic crystals, including strongly birefringent ones. The better sensitivity of TIL is demonstrated using the highly birefringent organic salt DAST (4--methyl stilbazolium tosylate).

We report a demonstration of an infrared focal plane array based on InGaAs/InGaP quantum dot infrared photodetectors. The middle-wavelength infrared quantum-dot infrared photodetector(QDIP) structure was grown via low-pressure metal organic chemical vapor deposition. A detectivity of was achieved at and a bias of −1.4 V. The background limited temperature of our QDIP was 140 K with a 45° field of view. A 256×256 detector array was fabricated with dry etching, and hybridized to a Litton readout chip by indium bumps. Thermal imaging was achieved at temperatures up to 120 K. At the noise equivalent temperature difference was measured as 0.509 K with a 300 K background and optics.

We have proposed a coherent control method that is available even for inhomogeneously broadened systems, which uses an area-regulated laser pulse sequence. It is expected to be applied to ultrafast optical devices without restriction of energy relaxation time.

High brightness (2 W with is demonstrated at 980 nm using a gain-guided tapered GaInAs/(Al)GaAs quantum-dot laser. A remarkable low temperature shift (0.09 nm/K) of the emission wavelength is observed. Moreover, at the emission wavelength is quasiconstant as a function of the injected current.

An ultracompact, multifunctional, and highly integrated photonic switch with a 3×2 configuration has been designed and fabricated with SiGe/Si material by using silicon-optical bench technology. This kind of switch can be used in fiber optic communicationssystems,photonic integrated circuits and wavelength division multiplexed networks as an optical power splitter, optical crossconnect, optical add-drop multiplexer, and wavelength division multiplexer simultaneously or individually. The function of the device is to combine multiwavelengths from different input channels and to switch them to different output channels. The operating wavelength range of the device is designed in band, i.e., 1530–1570 nm. The device was characterized at 1540, 1550, and 1560 nm wavelengths. The performance at these wavelengths is found satisfactory. The measured insertion loss is less than 2 dB, ON/OFF ratio is greater than 30 dB, crosstalk is between −20 and −25 dB, and switching speed is 100–200 ns.

Negative refraction can occur at the interface between vacuum and an indefinite medium—an anisotropic medium for which not all elements of the permittivity and permeability tensors have the same sign. We show experimentally and via simulations that a metamaterial composed of split ring resonators, designed to provide a permeability equal to −1 along the longitudinal axis, will redirect -polarized electromagnetic waves from a nearby source to a partial focus. The dispersioncharacteristics of indefinite media prohibit the possibility of true aplanatic points for a planar slab; however, by contouring the surfaces aplanatic points may be realized, as well as other geometrical optical behavior.

Morphological properties of Eu-doped GaNquantum dotsgrown by molecular beam epitaxy have been studied. Eu tends to segregate on the surface of AlN and GaN, leading to drastic changes in adatom kinetics. As a consequence, both size and density of Eu-doped GaNquantum dots strongly depend on the Eu flux used during the growth.

The phase transformation dynamics induced in films by picosecond laser pulses were studied using real-time reflectivity measurements with subnanosecond resolution. Evidence was found that the thermal diffusivity of the substrate plays a crucial role in determining the ability of the films to crystallize and amorphize. A film/substrate configuration with optimized heat flow conditions for ultrafast phase cycling with picosecond laser pulses was designed and produced. In this system, we achieved reversible phase transformations with large optical contrast using single laser pulses with a duration of 30 ps within well-defined fluence windows. The amorphization (writing) process is completed within less than 1 ns, whereas crystallization (erasing) needs approximately 13 ns to be completed.

GaN micro-light-emitting diodes (micro-LEDs) with monolithically integrated microlenses have been demonstrated. Microlenses, with a focal length of 44 μm and a root mean square roughness of ∼1 nm, have been fabricated on the polished back surface of a sapphire substrate of an array of micro-LEDs by resist thermal reflow and plasma etching. The optical properties of the microlenses have been demonstrated to alter the emission pattern of the LED emitters. The cone of light emitted from this hybrid device is significantly less divergent than a conventional broad-area device. This combination of micro-LED and microlens technologies offers the potential for further improvement in the overall efficiency of GaN-based light emitters.

We demonstrate the applicability of liquid-metal jets in vacuum as regenerative targets for laser-plasma generation of extreme ultraviolet(EUV) and soft x-rayradiation. This extends the operation of liquid-jet laser-plasma sources to high-temperature, high- high-density, low-vapor-pressure materials with new spectral signatures. The system is demonstrated using tin (Sn) as the target due to its strong emission around which makes the material suitable for EUV lithography. We show a conversion efficiency of 2.5% into and report quantitative measurements of the ionic/atomic as well as particulate debris emission.

Conversion efficiency and electron temperature scaling laws are experimentally studied in the wavelength-cubed regime, where a single-wavelength focus allows low energy pulses incident on a Mo target to produce x rays with excellent efficiency and improved spatialcoherence. Focused intensity is varied from to Conversion efficiency and electron temperature are best described by a power law for energy scaling while an exponential law best describes the scaling of these parameters with pulse duration.

The sequence of shape transitions in low mismatch, dilute coherent alloy islands was documented by scanning tunneling microscopy and cross-sectional transmission electron microscopy. In dilute islands we observe an extended shape evolution involving a new “barn” shape formed by introduction of steep {111} facets not observed at higher mismatch strain. This extended shape evolution implies a delayed onset of plastic deformation as a result of an altered competition between strain relaxation via coherent islands and the introduction of dislocations in this regime.

The standard parametrization of free carrier absorption in silicon predicting a linear dependence of the absorption on carrier concentration is revised, finding that due to several simplifications, it is only applicable up to carrier densities of about A parametrization applicable for both - and -type silicon and for doping densities as high as is introduced. Using this parametrization, considerably better agreement between the emitter sheet resistance of diffused layers measured by IR transmission and electrical measurements is found, proving the applicability of the enhanced model even for heavily doped layers. Additionally, parameters for the dependence of the refractive index of silicon on doping concentration are given.

ZnO is considered as a promising substrate for GaNepitaxy because of stacking match and close lattice match to GaN. Traditionally, however, it suffered from poor surface preparation which hampered epitaxialgrowth in general and GaN in particular. In this work, ZnO substrates with atomically flat and terrace-like features were attained by annealing at high temperature in air. GaNepitaxial layers on such thermally treated basal plane ZnO with Zn and O polarity have been grown by molecular beam epitaxy, and two-dimensional growth mode was achieved as indicated by reflection high-energy electron diffraction. We observed well-resolved ZnO and GaN peaks in the high-resolution x-ray diffraction scans, with no phase detectable. Low-temperature photoluminescence results indicate that high-quality GaN can be achieved on both O- and Zn-face ZnO.

Cathodoluminescence mapping reveals threading defects, frequently formed by the lattice misfit between GaN and sapphire substrate, as a dark contrast connected with changes in the energy state. Multiple quantum wells, 2.5 nm and 13.9 nm GaN layers, are resolved in the secondary electron image as well as in the backscattered electron image. The backscattered electron image, providing compositional mapping without surface effects such as cleaved steps, reveals the presence of V defects and confirms the thin six-walled structure of the V defect with InGaN/GaN layers. These scanning electron microscopy observations can be performed after very simple specimen preparation, namely just cleaving the sapphire substrate with the epilayers.

The deformation behavior of rapidly grown tetragonal (KDP and DKDP) single crystals, with a deuteration degree x of 0.0, 0.3, and 0.6, is studied by nanoindentation with a 1 μm radius spherical indenter. Within experimental error, the deformation behavior is found to be independent of the deuterium content and different for (001) and (100) surfaces. Multiple discontinuities (so-called “pop-in” events) in force-displacement curves are observed during indentation loading, but not during unloading. Slip is identified as the major mode of plastic deformation in DKDP, and pop-in events are attributed to the initiation of slip.

The effects of hydrogen and deuterium on ferromagneticGaAsdoped with high concentrations of Mn are studied. Secondary ion mass spectroscopy depth profiles show that D is incorporated in the same concentration as Mn. The epilayers change from metallic to semiconducting behavior upon hydrogenation. Fourier transform infrared absorption measurements show the As–H and As–D local vibrational modes characteristic for the complexes of hydrogen with group-II acceptors in GaAs.

In this letter, we report on temperature-dependent anti-Stokes photoluminescence (ASPL) at an interface between partially ordered epilayer and GaAs substrate. It is found that the intensity of the ASPL depends strongly on temperature accompanying with a clear blueshift in energy. A localized-state luminescence model was employed to quantitatively interpret temperature dependence of the ASPL. Excellent agreement between the theory and experiment was obtained. Radiative recombination mechanism of the up-converted carriers was discussed.